1. Field of the Invention
The present invention relates to an ignition device for providing laser ignition of an internal combustion engine.
2. Description of Related Art
A so-called laser ignition is known from published international PCT patent application WO 2005/066488 A1. This laser ignition includes an ignition laser, which extends into the combustion chamber of an internal combustion engine. The ignition laser is optically pumped by a pumping light source via a fiber optic guide.
At one end of the ignition laser facing the combustion chamber, there is a so-called combustion chamber window, which is able to transmit the laser beams generated for the ignition laser. This combustion chamber window has to be accommodated in a sealing manner in a housing of the ignition laser. There are high requirements on the sealing between the combustion chamber window and the housing, because during the operation of the internal combustion engine surface temperatures of more than 600° C. may occur at the combustion chamber window. In addition, there may also be intermittent pressure loads of up to ca. 250 bar. When an ignition laser is used for igniting a gas turbine, it is true that slight pressures prevail in the combustion chamber of the gas turbine, but the surface of the combustion chamber window may reach up to 1,000° C., and uncontrolled ignition by incandescence having to be controlled in every case.
It is clear that the inside of the ignition laser has to be reliably sealed from the extremely high temperatures and pressures. If exhaust gases should happen to reach the inside of the ignition laser, this would lead to failure of the ignition laser.
From post-published German patent application document DE 102007041528.3, an ignition laser is known in which the combustion chamber window and the housing are sealed in such a way that, over the entire service life of the internal combustion engine, and at the pressures and temperatures prevailing in the combustion chamber of an internal combustion engine, a secure and reliable seal of combustion chamber window and housing are ensured.